Where did you get those #s for Fed? He actually won 60.9% at '15 Wimby, barely more than Novak's 60.7% - in
the OE the only guy who came close to the rarefied 70% mark at SW19 is '84 Mac - while he lost the % game later at the USO, 63.4% to Nole's 64.7%. Excellent %s from both - for most top players making
the 60% Club is a rare achievement - but neither comparison shows a decisive advantage for Fed.
Two more problems with these comparisons. One, tournament %s don't tell us much due to their limited sample size, which is why I generally start from seasonal %s. You really should look at both - while there are cases like '11 Novak that peak too early there are also
opposite ones like
'15 Stan whose seasonal % (55.8% in his case) sees a dramatic increase (to 61.1%) at RG.
Two, GW%s tell us less about respective players as the surface in question gets faster. When an Ivanisevic's serve is clicking on grass your GW% becomes almost irrelevant, and the best you can do is to try to hold your own serve and wait for the eventual window to attack (easier said than done, of course, cuz guys like Goran, Krajicek and Stich can actually hurt you in a variety of ways unlike Karlovic and Isner). Obviously you can't do that on clay, at least not consistently, which is why I'm wont to emphasize its high margin for error when pointing to this or that GW%.
Also Rafa really started retooling his game as early as '07. Fedal fans like to trumpet his 81-win streak as proof of his younger self's superiority, but if you look at his early RG runs he was dropping sets to the likes of Grosjean, Mathieu and Hewitt, players that I rather doubt would've done the same vs. '10, '12, '17 or '18 Rafa (just to pick a few examples). It's easy to say he's become more aggressive because he's had to, but a more likely explanation is that he realized he could play more like (peak) Courier - that is, dealing painful body blows more than running everything down - without sacrificing much margin for error. Yes, the greater risks meant more losses and an end to another comparable winning streak, but they also meant greater rewards if he could strike the right balance between that extra aggression and his trademark topspin. It's safe to say he's been able to do just that when it counted most, again except in those lost years of '09, '15, '16 and '21.
Speaking of which that spin department is where
Novak happens to be literally average, on both wings. When I say he's a better "grinder" than Fed I'm referring as much to his mentality than to his actual CC game, which would normally feature crazier topspin for most elite dirtballers of yore. Of course the rest of his package - one of the best FH-BH combos ever, ATG movement and defense, relatively high shot tolerance - is still good enough to earn him many wins on clay, but that relative lack of weight behind his shots would prove fatal more often than not vs. fellow multi-FOers, especially if they can match his defense and court coverage like Rafa, Borg and even Bruguera all of whom boast ball-crushing topspin to boot.
People aren't taking into account this spin factor when they say peak Novak or Fed would be able to exploit geriatric Rafa's diminished defense and mobility. A lot easier said than done when Nadal would be pushing either guy further and further back with his Tysonified groundies. Both could try to counter that by taking the ball early, yes, but against such spin
and amped-up power on dirt? Doubt anyone but Agassi would be up to the task. The only other option I see is coming in at every opportunity, but this is different from regular S&V and apart from Mac it would take a specialized net rusher like Panatta or Noah to pull it off on this surface.
Again a 4-8% difference in seasonal GW% is a virtually impossible hurdle to overcome on clay, even more so at RG where the gap is likely to widen with the superior dirtballer holding nothing back. If we were talking an old-fashioned H2H series of say 10 matches I'd say prime Novak gets about 2 Ws. IRL over 4-5 FO SFs and Fs, though? Almost certainly zero.